In existing processes for manufacturing an oxide TFT array substrate, an electrode insulation layer is usually made of one of the following two kinds of materials. One is an inorganic material having a high dielectric constant, such as silicon nitride and silicon dioxide, but it is unable to suppress capacitance effect generated by electrodes to a relatively low level while improving a threshold voltage of the TFT. Moreover, the process for forming an insulation film of the inorganic material is complicated, and several times of deposition is needed to complete the formation of a thicker inorganic insulation film. The other is an organic polymeric material that has advantages of easily-controllable performance, easiness of processing, suitability for large-area production, etc., and that can be processed by a simple method such as spin-coating, coating or printing at room temperature, which significantly reduces production cost. However, since the dielectric constants of these polymeric materials are relatively low, when they are used alone to make the insulation layer of the TFT, a higher threshold voltage of the TFT will be required. This will cause bigger leakage current and thus affect the use of the polymeric material for the insulation layer of the TFT.